1. Field of the Invention
The invention relates to a cutting mechanism for devices for comminuting or reducing the size of material and products, particularly flat material layers, such as documents, etc.
2. Prior Art
Conventional shredding machines have two cutting rollers with meshing cutting disks between which a longitudinal material cut takes place to product strips parting. A cut, in which the strips are reduced to individual particles, is brought about in that slots are provided in the upper surfaces of the cutting disks into which the material is forced by the adjacent disk and is consequently broken down. These shredding machines, e.g. according to German Pat. No. 22 47 901, in which the slots on adjacent disks are in each case reciprocally displaced by a half pitch or spacing, operate in a completely satisfactory manner, provided that the particles can be long enough for the slot to be made sufficiently large compared with the slot pitch and the layer thickness is not so large that the slot can become clogged. If such a shredding machine is overloaded by excessively thick layers, then the breaking down of the strips into individual particles may not take place completely, at least on one side of the layer.
German Pat. No. 33 13 103, which has star-like teeth on both cutting disks, and British Pat. No. 1,392,319, which has numerous narrow, high, curved sawteeth, reveal similar systems with a "tooth on gap" alignment.
For the purpose of comminuting individual document portions, German Pat. No. 285,045 discloses the use of cutting disks, in which circumferentially distributed tips symmetrical to a radius of the cutting disk function in "tooth on tooth" manner, whereby they initially pass transversely through the document and then cut through the same longitudinally. However, for this purpose the document must be kept taut or rigid by a feed roller pair. As a result of this complicated construction and the limitation to single layer documents, this proposal has not been practically adopted and has been virtually forgotten.
An object of the invention to provide a cutting mechanism making it possible to also cut thicker layers of documents into particles, particularly shorter particles.
This object is achieved by use of two cooperating cutting rollers driven in rotary synchronized manner in opposite rotation directions, the rollers having alternating, overlapping cutting disks, each cutting disk of one of the cutting rollers engaging in a ring slot between adjacent cutting disks of the other of the cutting rollers, outer edges of each cutting disk forming two cutting edges and having on an outer circumference of the disk teeth defining tooth tips extending from tooth roots, the tooth tips being aligned and the disks being synchronized as driven such that on adjacent cutting disks two corresponding teeth are approximately juxtaposed in a longitudinal direction of the cutting rollers in a tooth-on-tooth relationship, the teeth being inclined forward in sawtooth manner pointing in the rotation direction of the corresponding cutting roller, the adjacent cutting disks of the two cooperating cutting rollers being positioned such that the teeth of the adjacent cutting disks overlap one another radially at said tooth roots. As a result of the "tooth on tooth" arrangement for adjacent cutting disks with a corresponding inclination of the teeth, the flat material layer is penetrated from either side by the teeth in a position ensuring optimum penetration. The center lines of the teeth are approximately in one plane and during the penetration do not move the material being cut outwards against the feed direction.
Thus, the device does not require leading feed rollers. In addition, the loading direction of the teeth during pushing through is largely central, i.e. virtually ideal, although this does not initially appear to be the case with pronouncedly forwardly inclined teeth. A further advantage is that the forwardly inclined tooth shape aids the removal of particles from the slot, in that the front tooth profile acts there in the manner of a shovel, which raises the particles out of the slot and therefore relieves any following strippers.
Further advantages and features of the invention can be gathered from the subclaims and description in conjunction with the drawings and the individual features can be realized in embodiments of the invention and in other uses either singly, or in the form of subcombinations.